Corrosion Mechanisms in Additively Manufactured 316L Stainless Steels

Additively manufactured 316L stainless steels (316L SS) using laser powder bed fusion technique (L-PBF) exhibit an excellent combination of high strength and ductility compared to the conventional counterpart. The outstanding material mechanical properties originate from the sub-grain cellular structures developed during the rapid solidification inherent to L-PBF. These structures consist of elongated cells decorated by high density of dislocations, trapped solute, and fine precipitates at their boundaries. The impact of such cellular structures on corrosion resistances, however, remains incompletely understood. In addition, the L-PBF process leads to high surface roughness and usually around 0.1 to 0.5% of porosity. However, the pitting potential of the L-PBF 316L SS can be an order of magnitude higher than the conventional, well annealed counterpart. In this talk, we will first present a detailed multi-scale characterization of the microstructural features unique to L-PBF 316L SS. In a second part, we will present our experimental-simulation integration approach where we combine surface chemistry mapping and electron and atomic force microscopy with multi-scale simulations to understand the effect of local microstructure variations on pitting and metal dissolution rates in NaCl and HCl environments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Authors acknowledge the support of the Laboratory Directed Research and Development (LDRD) program (20-SI-004) at LLNL.